The Butterfly Effect
by chromeknickers
Summary: When the tiniest variable disrupts the ordinary condition, the smallest differences arise, ultimately changing the outcome of fate. This is the so-called butterfly effect: where Sheldon and Penny's real story begins. But then again, reality is relative.


_**Warnings & Disclaimers**: This is my first TBBT fic, and it has some really lame physics jokes in it. Also, I do not own TBBT, nor do I profit from it. Pity. I'd really like my own Sheldon. =/_

**A/N:** This is an alternate version to S02E14's The Financial Permeability. Consider this a butterfly effect: where the tiniest variable has disrupted the ordinary condition, making it so that Penny seeks aid from Sheldon on an 'Anything Can Happen Thursday' – with Leonard and co in Vegas, leaving our favourite duo to their own devices. _(Another disclaimer: The opening exchange is a taken – paraphrased, cut out, and added to – from the Penny and Sheldon scene in the aforementioned episode)._

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"The one thing that chaos theory shows us is that for many simple mathematical relationships, the outcome of the operation of the explanatory variables is exquisitely sensitive to very small differences in the initial conditions under which the analysis was begun. This is the so-called 'Butterfly Effect'."*

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**The Butterfly Effect**

Was it really possible that a butterfly flapping its wings in Brazil could set off a tornado in Texas? Penny never really thought in terms of predictability or chaos – or in scientific terms at all, really – but she was convinced that her ex-boyfriend, Kurt, skipping on bail had led to her inability to pay last month's rent – and the month before that. Her gullibility and generosity, like the flap of a butterfly's wings, had led to her current monetary crisis: a financial tornado in Pasadena. Her only shelter: apartment 4A.

"Ooh ooh ooh," Penny called out to Sheldon, rounding the stairs two at a time once she spotted the lanky physicist open the door to his apartment. "Shut the door! Shut the door!"

Clad in a green Monsters t-shirt with a baby blue long-sleeved shirt underneath, pushed up his forearms, a puzzled Sheldon stepped to the side, letting his blonde neighbour whiz past him into his apartment. "Why?"

"Just do it!"_she ordered._

_Sheldon immediately did just that, shutting the door with a look of confused panic, locking himself outside with Penny inside. A heartbeat later, Penny opened the door, shook her head, and impatiently beckoned Sheldon inside._

_"_Get _inside_ and shut the door!" she ordered, stepping to the side to allow Sheldon access to his own apartment.

"Well, you didn't specify!" Sheldon complained petulantly, stepping inside.

Dropping his keys in the key bowl, Sheldon hugged his packet of Red Vines close to his chest and took out a stick of red liquorice to munch on. Penny immediately closed the door behind them and let out a laboured sigh, wringing her hands somewhat nervously.

"Where's Leonard?"

"He went to Las Vegas with Howard and Raj," Sheldon answered absently, holding up his liquorice before he took a bite. "It's 'Anything Can Happen Thursday'."

While he was talking, Penny bent down and placed her ear against the surface of the door. Nonplussed, Sheldon slowly shuffled towards her and emulated her action, putting his ear against the door – unsure of what the results of this experiment would yield.

After a moment, Sheldon stood back and glanced down at Penny's back, regarding her with deep blue eyes. "I'm sorry, Penny, but I don't understand the social situation here." He cracked his liquorice at her like a whip. "Could you give me a point of reference on how to proceed?"

Rolling her eyes slightly, Penny stood up and let out a sigh, turning to face her neighbour. "The building manager's showing an apartment downstairs," she explained with another laboured sigh, lifting her hands in futility, "and I haven't paid my rent."

"Oh, I see..." Sheldon said almost sympathetically in one breath while continuing with another, "Penny, I'm not sure I'm comfortable with harbouring a fugitive from the 2311 North Los Robles Corporation."

Penny's shoulders sagged forward. "Sheldon, it's no big deal," she said not too convincingly, wringing her hands in nervous frustration. "I'm just a little behind on my bills because they cut back my hours at the restaurant, and my car broke down, and..."

"And...?"

"Well," Penny began, her voice pitching an octave higher, "I kinda lent eighteen-hundred dollars to Kurt. He had a bunch of outstanding tickets and a bench warrant, so I, you know, paid his fines."

She offered him a sheepish grin, but Sheldon merely shook his head, turning around to walk over to the coffee table, setting down his packet of Red Vines.

"Penny, you really shouldn't lend money to that thug," he admonished, taking a bit out of his liquorice. "You can barely support yourself."

"I know," Penny agreed all too readily, taking a seat on the arm of the sofa. "I'm an idiot." She clasped her hands together and gave him a hopeless look. "Plus, my stupid engine ended up costing me twelve-hundred dollars to fix, and...I just have no more money."

Sheldon brought the stick of liquorice down from his mouth and rocked on his feet, as though a brilliant idea had suddenly struck him. "You know, it occurs to me you could solve all your problems by obtaining more money."

Penny glanced up Sheldon, blinking slowly, unimpressed. "Yes, that occurs to me, too."

"Hang on a moment."

Sheldon set down his liquorice and made a light sprint towards the bookcase behind the sofa. Penny stood up and turned around, watching him retrieve a jar off the top. With a twist, a yellow and red snack escaped the jar, causing Penny to let out an 'Oh' of surprise. Sheldon then placed his hand in the jar and pulled out a large wedge of cash.

_"_Here," he said, holding the money out to her. "Take some. Pay me back when you can."

"Wow, Sheldon," Penny said, a look of shock and wonder lingering on her face, "you've got a lot of money in there."

Sheldon nodded. "That's why it's guarded by snakes," he answered simply, and then offered the money again. "Take some."

"Sweetie, don't be silly."

Sheldon shook his head, looking serious. "I'm never silly." He held his hand out – again. "Here."

"Sheldon, I-I can't," Penny said, waving her hands uncomfortably.

"Don't you need money?"

"Yeah, but…"

"You need money, and this is money I'm not using," he reasoned simply with a slight shrug of his shoulders. "Take it."

"...Okay," Penny said after a moment's pause, offering Sheldon an awkward but endearing smile.

Instead of handing her a few bills, Sheldon gave her the entire wad of cash, placing it in her trembling hands. This was more than any one had ever done for her, and Dr Wackadoodle was the last person Penny expected such generosity from – especially without any strings attached. This was a Sheldon she had never seen before, and she liked this side of him.

"Thank you, Sheldon," she said, a hint of emotion tinting her voice. "This really means a lot to me." Holding the money close to her chest, she couldn't help but deepen her smile, nodding gratefully at her socially awkward friend. "I'll pay you back as soon as I can."

"Of course you will," he said with an upward inflection. "It's impossible to pay me back sooner than you can – assuming you subscribe to a linear understanding of time and causality."

"Right," Penny said, walking toward the door, intent on paying the building manager as soon as possible.

Once she grasped the handle, she turned around, giving Sheldon her most winning smile.

"Uhm, Sheldon? Can I make you dinner tonight?"

"Can you?" he asked with a drawl, looking at Penny as though he was about to give her a lecture on grammar.

"_May_ I make you dinner tonight?" she corrected, her smile never faltering.

"I suppose so," he relented, stalking over to where she stood in order to pick up his released snakes and put them back in the jar. "It is 'Anything Can Happen Thursday'."

Penny's smile widened, and she leaned forward, placing a hand on Sheldon's arm. "It's a date."

**-x-**

"Sheldon, are you ready to _par_-tay?"

Penny walked into the apartment with a big grin on her face, dangling several grocery bags in the air that were filled with food and alcohol. She had changed into her usual attire at night: a solid colour tank top – yellow – and matching short shorts.

"Penny," Sheldon began, looking up from his laptop, "I'm unclear if you are trying to engage in conversation about golf or the British ophthalmologist Warren Tay."

"What?" Penny asked, furrowing her brow as she walked over to the kitchen, setting the bags on the counter.

"What do you need clarification on, the term 'par' in golf or Warren Tay's work on autosomal recessive genetic disorders?"

Penny blinked several times and stared at Sheldon blankly. Not averting her gaze, Sheldon eyed Penny intently, waiting for a response – the corner of his lips twitching.

Breaking the stare-off, Penny shook her head, golden curls bouncing. "No, no, Sheldon," she said. "'Par-tay' is slang for party."

Sheldon raised a dark eyebrow quizzically in the air. "I thought we were having dinner, not throwing a social engagement." He pursed his lips and wrinkled his nose in annoyance. Then both eyebrows shot up in contemplation. "Is it someone's birthday again?"

He glanced about the room, checking for party favours and presents – and possibly guests hiding behind furniture. Penny merely smirked and leaned forward, resting both hands on the kitchen counter-top.

"How about some spaghetti?" she asked, changing the subject. It was fruitless to let Sheldon continue with his diatribes or attempts at understanding slang – and sarcasm.

Sheldon's head swung back around, and he placed his laptop on the coffee table, offering Penny a childish expression of barely suppressed glee. "With little cut up hot dogs?"

"Of course," she said with a smile, reaching inside one of the plastic bags to hold up a package of hot dogs for Sheldon to inspect.

He immediately sat up in his seat. "In Mama Italia marinara sauce?" he added hopefully, turning at an unnatural angle on the sofa.

"Mhm," she hummed, taking out the bottle of sauce and placing it on the counter.

After paying her landlord, Penny had made it a point to call Sheldon's mother – to ask her what kind of foods Sheldon liked. Mary had eagerly supplied Penny with the simple ingredients for her son's favourite dish, and Penny was more than happy that it was something she could easily make.

Sheldon grinned maniacally and clapped his hands together. "I'm in for a real _eye_-talian treat!"

Penny giggled and knelt down on the floor, checking the lower cupboards for the pots and pans she needed. "Yes, you are, Sheldon."

While Penny cooked, Sheldon surfed online. Both hummed a sea shanty – Drunken Sailor – nodding their heads to the beat of the song, exchanging glances as one fed the other his or her next line.

"So, what did you want to watch tonight?" Penny asked once they had finished their song.

"I was thinking we could watch _Firefly_," Sheldon suggested, closing his laptop as he stood up to walk over to their DVD collection. "Would you be adverse to watching the entire season? It's only fourteen episodes."

"Sounds like fun," Penny said, mixing the chunks of hot dog into the sauce, stirring slowly. She then took out two plates and two pairs of forks.

Sheldon frowned and picked out the DVD package, popping one of the discs into the player. "I think you mean 'this should be fun'."

"Whatever," Penny said, rolling her eyes as she dished out the pasta. She then picked up both plates and handed one to Sheldon. "Here's your _eye_-talian meal."

Sheldon eagerly accepted and returned to his spot on the sofa, while Penny took a seat on the chair next to him.

"Mmm, I love spaghetti with little hot dogs," Sheldon said with a child-like smile, sitting forward and putting his nose near the dish, taking in its aroma. "Thank you, Penny."

Penny smiled at the sincerity of his tone, her green eyes squinting like upside-down smiles. "You're welcome, sweetie."

"No more chit chat," Sheldon clipped, sitting back in his chair and digging into the spaghetti. "I'm eating."

Penny stared at Sheldon pointedly, twisting her lips into a frown before she breathed out sharply through her nose, turning back to her own plate.

Sheldon pressed play on the _Firefly_ DVD, starting with the 'Serenity' episode. The two merrily ate their dinner in silence, engrossed in the series. Once their food was consumed and Sheldon was pressing play on 'The Train Job' episode, Penny took their plates over to the sink and then fished through one of the other plastic bags she had brought: the one containing all the alcohol.

"Did you want something to drink, honey?" she asked, pulling out a bottle of vodka and two shot glasses.

"I have my milk," Sheldon said distractedly, holding up his glass of milk while staring intently at the television screen.

Penny snorted and shook her head, setting down the liquor bottle to twist off the top. "No, I mean, do you want something alcoholic?"

"No, thank you."

Penny walked over to the cupboard and took out two large tumblers, pouring three fingers of vodka into one of the glasses, and then took a cartoon of orange juice out of the plastic bag, opening it up and topping off her screwdriver.

"Are you sure?" she asked, licking the juice off her fingers. "I brought vodka, rum, tequila, and kahlua."

Sheldon glanced up from the screen and shot an inquisitive look Penny's way, raising a dark eyebrow in mild interest. "Are you planning to consume all of that alcohol tonight?"

Penny took a sip from her screwdriver, pursing her lips together and looking pensively at the tall brunet. "Maybe not tonight," she answered, bringing the tumbler to her lips to hide her smirk. "I might finish the rest in the wee hours of morning."

Sheldon gave her a withered look before he turned his attention back to _Firefly_.

Draining half her glass in one gulp, Penny set down the tumbler and fingered the small bottle of kahlua, slipping it out of the bag. A devious thought came to mind as Penny drained the rest of her glass. It had occurred to her that Sheldon was actually quite entertaining when he was drunk – singing 'To Life' from _Fiddler on the Roof_ and other Hebrew songs, and being generally boisterous in a less annoying way that usual. She wondered what he'd be like alone with her – drunk and alone. Would he loosen up again? Would he be just as fun?

"Hey, sweetie," she began innocently, pouring herself another drink, "would you like me to make you some hot cocoa?" The alcohol was already beginning to effect her; heat was flooding her cheeks.

Sheldon turned his head to regard Penny with his deep blue eyes, his interest piqued. "_Homemade_ hot cocoa?" he asked hesitantly, a sanguine look settling on his square, angular face.

"Mhm," she answered with a nod, taking another sip of her drink and hissing through her teeth (she may have put more than three fingers of vodka in the glass this time around).

Sheldon seemed to contemplate her suggestion for a moment and reached down to pick up the remote, putting the show on pause.

"Would you make it like my Memaw does?" he asked in his soft man-child voice, reminding Penny of an adorable little boy asking his mother for sweets.

Penny licked her lips, smiling smugly at the genius of her plan, which was falling perfectly into place. "Do you have the recipe?"

"Yes," Sheldon answered, nodding emphatically. "It's in the recipe box, under C." He held up a long arm, pointing an equally long finger at the cupboard behind her.

Turning, Penny walked over to the cupboard and located the recipe box, taking out the appropriate index card. Satisfied that Penny had located his Memaw's recipe, Sheldon resumed the _Firefly_ episode. Once his attention was diverted, Penny set her nefarious plan in motion, retrieving the needed ingredients and pots. Following the instructions exactly, Penny stirred in the 'special' ingredient – a shot of kahlua – and then poured the spiked hot beverage into Sheldon's specially designated hot cocoa mug.

"Did you following the directions?" Sheldon asked condescendingly, not bothering to turn his head as Penny brought over the drink.

"Yes, Sheldon," she droned, standing in front of him, offering him the drink.

Sheldon looked up at Penny with his big cerulean eyes, finally acknowledging her existence. "Heated to 180 degrees?"

"_Yes_, Sheldon," she answered tersely, behind gritted teeth.

"Are you sure?" he asked with doubt, tilting his head to side. "Did you test it?"

Penny bit her inner cheek in frustration, trying to keep her temper in check. "I can test it by pouring it on your lap," she offered with a glare, shoving the drink in his hands.

Sheldon blinked rapidly and took the mug, turning his head to pout. "Well," he said, exasperated, "you don't have to be mean."

Penny walked back over to the kitchen counter and grabbed the bag with all the alcohol in it. She then brought it all into the living room and placed the bag on the coffee table, glass bottles clinking together.

Entranced with the television and the hot cocoa, Sheldon barely paid attention to Penny setting up bar right in front of him. Settling into the spot next to Sheldon on the sofa, Penny brought the tumbler of vodka and orange juice to her lips and took a sip, eyeing Sheldon with unmasked interest.

"Mmm, this is rather good, Penny," Sheldon said with an upward inflection, licking his lips in satisfaction. "It's not quite the same as Memaw's, but I didn't expect you to get it exact."

"Thanks, I think," Penny said dryly, smiling into her drink – glad that Sheldon was none-the-wiser of the cocoa's alcohol content.

In little time, Sheldon was already at the bottom of his cup, tipping it back so that he could catch the last few drops. He lowered his head and licked his lips, casting Penny a shy smile.

"Can I have another one, Penny?" he implored, holding up the empty mug. "_Please please please_?"

"Of course, Sheldon," Penny said with a smirk, offering the lanky physicist a wink as she took his cup and slowly sauntered towards the kitchen.

Several consumed cups of kahlua hot cocoa later, Penny and Sheldon were curled up on the sofa, clinking glasses as they watched yet another episode of _Firefly_.

"Oh, I love this part!" Penny exclaimed excitedly, leaning forward to pick up the remote, turning up the volume.

"Jayne!" she crooned, leaning her head against Sheldon's shoulder. "The man they call Jaaaaaaaaaayne!"

Sheldon eagerly shot up in his seat. "He robbed from the rich, and he gave to the poor," he joined. "Stood up to the man, and he gave him what for."

"Our love for him now ain't hard to explain."

"The hero of Canton," they sang together. "The man they call Jaaaaaaaaaaaaaayne!"

Giggling and cackling respectfully, Penny and Sheldon exchanged meaningful glances and sang along with the show.

"I'm thirsty still," Sheldon complained after their sing-a-long, scooping chocolate liquid onto a long finger and greedily sucking it off.

Penny couldn't help but laugh. This was so not the Sheldon she was used to. He really did loosen up while drinking. He was normal; in fact, he was downright fun.

"Here," she said, grabbing a shot glass and filling it with the vodka.

Sheldon let out a disturbingly evil giggle (if there were such a thing) as the alcohol sloshed over the rim of the tiny glass. Normally, Sheldon would have pitched a fit at such an action, but in his current inebriated mind, everything was fine – including spilt alcohol and the mess that was now his living room.

He picked up the shot glass with slender fingers and downed the alcohol with ease, as though he had been doing this all his life.

"Smooth," he hissed through his teeth, slamming the glass back on the table, waiting for Penny to refill it.

After a few more shots, Penny poured herself another and watched with amusement as Sheldon opened the bottle of rum and began to swig it back like it was water.

"Want to play a game?" she asked, playfully tapping her head on Sheldon's shoulder, turning her face upwards so that she could look up into his startling blue eyes.

Sheldon blinked several times, nonplussed with the intense look that she was giving him, but did not stiffen under her gaze or her touch – not like he would have if sober.

"It depends on what kind of game," he said, licking his lips as he placed the rum bottle back on the table. "Did you know that the origin of the word game came from—"

"A _drinking _game," Penny suggested, interrupting Sheldon as she sat up straight and placed her hands on her lap, looking up earnestly at him. "Let's play a drinking game."

"What are the parameters?"

"Para-what?" Penny asked, furrowing her brow and dropping her shoulders – mouth wide open.

Sheldon was about to repeat his question when Penny shook her head, putting a hand on Sheldon's knee.

"Listen," she said, using her free hand to point at the television, "how about every time someone speaks Chinese on the show, we take a shot?"

"Mandarin."

"Hmm?" Penny asked lazily, her hand still on Sheldon's knee – and Sheldon still not flinching.

"Every time someone speaks _Mandarin_ on the show, we take a shot," he clarified, effectively correcting her ignorance of the different Chinese languages and dialects.

"Yes, fine," she breathed, annoyed. "Whatever."

**-x-**

"So, two atoms bump into each other, and one says, 'I think I lost an electron!' The other asks, 'Are you sure?' To which the first replies, 'I'm positive.' _Bazinga_!"

Penny snorted, draining her glass dry. "You're one funny wackadoodle."

Penny and Sheldon had quickly given up on the drinking game and had begun singing showtunes instead. Sheldon sang a lovely rendition of _Fiddler on the Roof_, while Penny danced animatedly in her seat.

"Okay, so what should we do now?" Penny asked, hiccupping softly as she leaned into Sheldon's shoulder.

Swaying into her side and then abruptly sitting upright, Sheldon held up a long index finger in silent declaration, stabbing it in the air as though he could bayonet his thoughts for Penny to read.

"I know," he said, still jabbing away as he turned his head to give Penny a mischievous grin. "Let's prank call Leonard!"

"Oh my God!" Penny cried, gobsmacked, slapping her palms against her flushed cheeks. "That's brilliant!"

"I know!"

Penny immediately shoved her hand into her shorts' pocket, fumbling around for her phone. Pulling it out, she blinked blearily at the screen, trying to focus on the names and numbers, searching for Leonard's. After slapping away Sheldon's hand a few times (he was insistent that his sight was not compromised), she managed to locate Leonard's number and pressed the call button.

"It's ringing!" she announced excitedly, covering her palm over the mouthpiece as she shared an impish grin with Sheldon.

"Penny, let me—"

"Shh!" she hushed, swatting away Sheldon's persistent hands.

_Hello?_

"Hello, is this Len—Dr Len Hof-sta...Hod-staff...Is this Leonard?"

_Uh, yes?_

"I...This is—"

"Penny!"

"Shh! Shut up!" Penny admonished, covering the mouthpiece again to shoot Sheldon a murderous glare. "I'm trying to talk."

"But, you're doing it all wrong," Sheldon countered nasally, scooting closer so that he could retrieve the phone.

_Penny? Is that you?_

"Oh my God!" Penny cried in horror, instinctively hiding the phone underneath her thigh and looking wildly up at Sheldon. "He knows it's me!"

Sheldon clenched his fists together and looked the other way. "Drat! He's more perceptive than I had imagined!" Uncurling his long fingers, he turned back towards Penny and impatiently held out his hand. "Here, give me the phone."

Penny hesitantly sat up and removed the phone from underneath her, handing it over to a very inebriated Sheldon.

"Hello," Sheldon began in a slow, controlled voice, "is this Dr Leonard Hofstadter?"

_Sheldon? _

Sheldon put his hand over the mouthpiece and smiled smugly at Penny, whispering, "He doesn't have a clue."

Penny gave him an encouraging thumbs up.

"Yes, Dr Hofstadter," Sheldon continued, sitting back in his seat, "I'm calling in regards to your exercise regimen."

_What? What is going on with you two? Put Penny back on the phone. _

"Is it true that you ran a lot in your youth?"

_Shel—_

"You do realise that the faster you run, the shorter you become! _Bazinga_!"

_Click._

Snickering, Sheldon closed the phone and turned to look expectantly at Penny, who offered her hand for a much-anticipated and much-deserved high-five, which he eagerly – if not somewhat awkwardly – accepted.

"Sheldon, you bad ass," Penny said with a sly grin, leaning forward to pick up her glass and have another swig.

"I am bad to the bone, Penny."

Penny snorted and took the phone from Sheldon's hand, resting it against her bottom lip with a contemplative expression on her face.

"So, who do you think _I _should call?" she asked, flipping open the phone.

And after five more prank calls – Penny's involving word association and the gratuitous use of 'Amanda Huginkiss' and Sheldon's complicated physic jokes – the two settled back down on the sofa, cackling madly to one another over their comedic pranking success.

"Shot time!" Penny suddenly sang, opening the bottle of tequila and pouring it into the two shot glasses.

"Shhhhhhot time!" Sheldon repeated, sitting up in his seat and placing his hands patiently on his lap.

"One sec," Penny said.

Stumbling to her feet, she haphazardly made her way around the coffee table towards the kitchen, extracting a sharp knife from the drawer and a lime from one of the grocery bags.

"Okay, Sheldon," she said, quickly cutting up lime wedges and placing them on a plate, "we're going to try some tequila."

"Te-keeeeeeeeeey-la!" Sheldon mimicked exuberantly, a lopsided grin hanging off his lips as he regarded the blonde with glazed-over eyes.

Giggling, Penny grabbed the salt shaker and the plate of lime wedges, walking back over to the sofa and settling in beside Sheldon.

"Alright, sweetie," she began, setting the limes and the salt next to the already poured shots, "I'm going to teach you how to do shots of tequila."

"Te-keeeeeeeeeey-la!"

"Yes, Sheldon," Penny agreed, rolling her eyes, "tequila."

"Te-key—"

Penny immediately put a finger to Sheldon's lips, effectively silencing him. "Say that again, Sheldon, and I'll go junior rodeo on your ass. Understand?"

"Yes," he replied meekly, shrinking back.

"Okay," Penny smiled brightly, as if she hadn't just threatened him. "First you lick the salt."

Licking at the knoll of her thumb, Penny shook some salt on it and then set the shaker down, looking up at Sheldon to make sure that he was paying attention. Seeing his eyes zeroing in on her thumb, Penny licked the salt and reached over to grab the shot of tequila.

"Then you take a shot," she said, quickly draining the glass and slamming it back down on the table, shuddering slightly at the acridity of the liquor. "Then you bite the lime and suck on it."

Penny popped the lime wedge into her mouth and greedily began sucking, getting the bitter aftertaste of the tequila off her palate. Once dry, she threw the empty peel in the plastic bag on the table and gave Sheldon a characteristic smirk.

"Got it?"

"Penny, Penny, Penny," Sheldon began, causing Penny to stifle a giggle. "I'm a physicist. I—"

"Yeah, yeah," Penny interrupted, pushing the salt and the tequila towards him. "Now take the shot."

Sheldon quickly obeyed, licking the knoll of his thumb, shaking the salt on it, licking it off, downing the shot, and then quickly biting down on the lime.

"Blegh," he said, shaking his head as he spit the lime out onto his hand and chucked it into the plastic bag.

Penny clapped, impressed that he didn't spit the alcohol out with the lime. It wasn't exactly a pleasant tasting liquor, and she wasn't sure if Sheldon was the type to have an iron stomach. She highly doubted it.

"Okay, now we're going to try this the _fun_ way," she told him, emphasising the fun.

"There's another ritual involved with consuming this libation?" he queried, a dark eyebrow seeming to disappear high into his hairline.

Penny nodded. "I'm going to lick the salt off your neck—" she pointed to his neck "—_then_ do a shot, and then bite the lime."

Sheldon's brow creased in uncertainty. "That can't possibly be sanitary, Penny," he stated with a slight lisp, almost recoiling at her advance.

"Sheldon," Penny began in a somewhat soothing tone, tilting her head and offering him a reassuring smile, "the alcohol will kill the germs."

Sheldon considered this explanation for a moment and then curtly nodded his head. "Touché."

Grinning at her small victory, Penny leaned in close. Her hot breath on his neck sent shivers down Sheldon's spine, and his body stiffened. The tendons on his neck stood out, but he waited patiently as she stuck her tongue out and flicked it along his neck, causing him to shudder involuntarily.

"Are you done now?" he asked quickly – nervous and uncomfortable – and she grinned against his neck.

"I haven't put on the salt yet," she said in a somewhat husky voice, amused by Sheldon's little idiosyncrasies returning, despite him being especially inebriated. Sober, he would have never permitted this behaviour. _Never_.

Penny took the salt and shook it on his neck, causing him to slap at his neck and let out another disturbing giggle. Fun, silly drunk Sheldon had returned.

Slowly licking the salt off his neck, Penny felt Sheldon's body instantly relax under her ministrations, tensing only briefly, like one being tickled. She let her tongue linger on his neck for a mississippi or two, enjoying the texture of his skin, his taste mixed with the salt. Then she sat back, downed the shot, and shoved a lime wedge into her mouth, sucking noisily as she watched Sheldon's body still reacting to her touch.

He was looking at her strangely, intently. His eyes were slightly glazed over from the alcohol and something else – something she couldn't quite put her finger on. Maybe it was that his eyes weren't completely unfocused: there was an intensity behind them – almost smouldering – as he gazed down at her lips.

She licked her own lips in return, nervously. Blinking slowly, Penny found herself lost in those intense blue eyes of his, and then she let her own gaze travel downwards to his lips.

"Penny?" a voice came out of the haze – Sheldon's – and Penny cleared her throat uncomfortably, shaking her head as though she could shake off the disturbing cobwebs of her meditations.

"Your turn, Dr Wackadoodle," she said, coughing, offering him an impish grin.

She licked her hand and wiped it along her neck. Reaching down, she picked up the salt shaker and shook it on her neck, giggling as the granules of salt tickled down onto her shoulders and down her top.

"Now _you_ lick the salt off my neck, here—" she pointed to her neck, grinning "—then you take a shot, and then you you bite the lime."

Sheldon looked at her neck and then looked at the shot glass, scooting closer to Penny so that their knees touched. Penny found herself feeling especially nervous and anxious, and she didn't know why – at least she didn't want to admit why. So she reached forward and grabbed a lime wedge off the plate, intent on handing it to Sheldon after he took the shot. Really, she just needed something to hold onto while she anticipated his tongue on her neck.

She shivered slightly when he leaned in, his long fingers touching her neck, pushing away errant strands of wavy blond hair to give him access to her exposed flesh. She breathed in sharply when she felt his soft lips on her neck, his breath hot on her skin. She moaned when she felt his tongue slide up her neck, her eyes rolling back into her head.

Feeling the loss of contact, Penny opened her eyes to see Sheldon reaching down to pick up the shot. When Sheldon had finished, setting the glass down, he glanced up at her, seeing the lime wedge lodged between her lips. Blinking in confusion and then in realisation, he leaned forward, taking the lime from Penny's mouth.

As Sheldon went to sit back, Penny reached forward with both hands and put them behind Sheldon's neck, pulling him downward. Turning her head and quickly spitting out the lime, Penny turned her attention back to Sheldon, pressing her lips firmly against his. And at first there was nothing – just two sets of lips pressed against each other. But then, after a pregnant pause, there was a hackling, barely perceptible change in Sheldon; slightly parting his lips, he tilted his head to the side, accommodating the angle of Penny's mouth on his.

Closing her eyes in turn, Penny decided to take the plunge and slid her hands up from around Sheldon's neck to his cheeks, holding his face in her hands as she hesitantly darted the tip of her tongue past his parted lips. Moaning softly, she felt his large, soft hands tentatively reach up to touch her own cheeks, cupping her face as he leaned forward, surely returning the kiss.

As butterflies fluttered in her stomach, Penny felt her head grow light as air. And though the kiss itself was brief, it seemed to last a life time in Penny's mind – the sensation of Sheldon's soft lips pressed against hers was so overwhelming that she drew back, breathless. Taking in a hitched breath of air, she bent forward and rested her forehead against his, breathing heavily as her mind swam with thoughts that she couldn't possibly begin to decipher.

"Penny?" Sheldon asked in a soft, hesitant voice, slowly pulling away.

Penny couldn't help but smile and opening her eyes, touching her fingers to his cheek. "Yes, sweetie?"

Sheldon's face scrunched up, and he rocked forward. "I think I'm going to vomit."

And with that, Sheldon jumped up and ran towards the bathroom, slamming the door shut behind him.

"Wonderful."

**-x-**

Twenty minutes had passed, and Sheldon had not returned to the living room. Concerned, Penny got up and went to the kitchen, taking a tall glass out of the cupboard and filling it with water. Quietly making her way to the bathroom, she found it deserted and figured Sheldon had gone into his room. Not bothering to knock, she opened the door and stepped inside.

"Sheldon?"

"Penny?" Sheldon asked from the darkness of his room, sitting up in his bed. "You're in my room – no one's allowed in my room."

"Yeah, I know, honey," she said calmly, holding out the glass of water as a manner of placating him. "I just wanted to check on you and see if you were okay – and to bring you some water to drink." She sat down beside him on the edge of the bed and put a hand on his forehead, checking for a fever (just in case) as she offered him the glass of water. "You need to remain hydrated."

Sheldon sat up and took the proffered drink, draining half of it and then handing it back to Penny so that she could set it on the night table beside the bed.

"Thank you, Penny," he said, licking his lips and turning his head, sinking back under the covers. "I'm tired. I'm going to bed."

"Oh," was all that Penny could say, frowning to herself as she drew back.

She should have known that a normal evening with Sheldon could never happen. Once sobered – or at least having thrown up – Sheldon had returned to his normal antisocial self, predictably banning her from his room.

She slowly rose to her feet, gently patting Sheldon's arm through the comforter, and turned towards the door. Perhaps she'd clean up before she left. She wouldn't want a strike against her come morning when Sheldon woke up and discovered the mess, subsequently suffering a stroke or an aneurysm.

"Penny?"

His voice was soft and almost painful to hear – like the sound of a wounded animal. She turned around, unable to resist, and saw that he had sat up a little, leaning his shoulders and back against his pillow.

"Yes, sweetie?"

"No one's allowed in my room," he reiterated, but his voice this time was gentle not harsh nor authoritative.

"Okay," she said, smiling sadly, turning back to reach a hand out to open the door.

"Penny?"

She turned around again.

"Could you sing Soft Kitty to me?"

In the dim light, she could see his big round eyes staring at her intently, imploring her to grant him this one wish. She felt her heart twist in her chest, and she relented, like she knew she would. This was Sheldon, after all. Letting out a sigh of defeat, Penny – the glutton for punishment that she was – closed the door behind her and walked back over to the bed, sitting directly beside him, on top of the covers.

"But Soft Kitty is only for when you're sick," she said, reaching out to smooth his hair back.

"Penny?"

"Yes, Sheldon?"

"I just vomited."

"Right," she said with a laugh, brushing his hair away with her fingers.

She scooted closer, putting her arm around his head and shoulders as he settled comfortably in his bed, drawing the covers up to his chin. Locking her other arm around neck – his shoulder resting on her abdomen – Penny effectively held Sheldon, rocking him slowly as she began to sing.

"Soft kitty, warm kitty – little ball of fur. Happy kitty, sleepy kitty – purr, purr, purr."

After a moment of silence, she rested her cheek on top of his head, hearing him breathe slowly and contently. She, too, she felt herself begin to grow tired, threatening to drift off to sleep in Sheldon's bed with her arms wrapped around his neck and shoulders.

"Thank you, Penny," Sheldon said softly, jerking her awake.

"You're welcome, sweetie," she said with a yawn, turning her cheek so that she could kiss the top of his head.

She slid down further, resting her head on his shoulder as she curled her body towards him, draping an arm lazily over his chest. She waited for him to tense up, to yell at her and kick her out, but he didn't. Instead, he slipped a hand out from underneath his comforter and gently rested it on her forearm, squeezing it once before they both drifted off to sleep.

**

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**Author notes: **I will most like expand on this at a later date – incorporating all the popular Shenny moments and applying the Butterfly Effect to them. But, for now, this will remain a one-shot. You'll notice how I weaved elements of The Maternal Capacitance (S02E15) into this, thus changing the canon of TBBT (at least for my 'verse). ^_^

By the way, if you didn't get Sheldon's prank call and what it had to do with physics, you're not the only one. If you want an explanation, PM me. :P

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*******Chaos, complexity, and sociology: myths, models, and theories **by Raymond A. Eve, Sara Horsfall, Mary E. Lee (xxix).


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